Vibration Evaluation Of Aircraft Propellers

Noise and building vibrations were measured for a series of helicopter and propeller-driven aircraft flyovers at WFF during May 1978. The building response data are compared with similar data acquired earlier at sites near Dulles and Kennedy Airports for operation of commercial jet transports, including the Concorde supersonic transport. Results show that noise-induced vibration levels in windows and walls are directly proportional to sound pressure level and that for a given noise level, the acceleration levels induced by a helicopter or a propeller-driven aircraft flyover cannot be distinguished from the acceleration levels induced by a commercial jet transport flyover. Noise-induced building acceleration levels were found to be lower than those levels which might be expected to cause structural damage and were also lower than some acceleration levels induced by such common domestic events as closing windows and doors. Shepherd, Kevin P. and Hubbard, Harvey H. Langley Research Center RTOP 535-03-11-03...

This book explains the accident involving Atlantic Southeast Airlines flight 529, an EMB-120RT airplane, which lost a propeller blade and crashed near Carrollton, Georgia, on August 21, 1995. The accident killed 8 people on board. Safety issues in the report focused on manufacturer engineering practices, propeller blade maintenance repair, propeller testing and inspection procedures, the relaying of emergency information by air traffic controllers, crew resource management training, and the design of crash axes carried in aircraft. Recommendations concerning these issues were made to the Federal Aviation Administration.

Summary: Vibration tests of a four-blade single-rotating propeller operating in a simulated pusher condition were performed because the combination of wake and downwash behind a wing was expected to provide serious excitation for reactionless vibrations of propellers with four or more blades. The tests were conducted in the LMAL 16-foot high-speed tunnel with a wing mounted at thrust-axis level ahead of the propeller; the blade sections at three-fourths the propeller radius operated at approximately twice their chords behind the trailing edge of the tapered wing at their closet position. Measurements of propeller vibratory stress were made for various airspeeds, engine speeds, and engine powers.